When star NFL running back Adrian Peterson was a kid in Texas, his father confronted him one day after football practice. Young Peterson had been disruptive in class, USA TODAY’s Josh Peter reports, so his father pulled out his belt and whipped him in front of more than 20 other students.

No one told authorities about that incident, or about the many other times Peterson’s father disciplined him with a belt or a “switch” cut from a tree branch. More than a decade later, though, standards have changed, and for the better. The 29-year-old star stands charged with a felony for whipping his own 4-year-old son with a switch, leaving ugly welts.

Peterson, now apologetic, says he was just doing what worked on him. “I have always believed that the way my parents disciplined me has a great deal to do with the success I have enjoyed,” he says.

That explains his behavior. It’s accepted wisdom that people do what has been done to them, whether it’s disciplining kids or beating up a spouse. But the explanation doesn’t excuse his actions. There’s a line between acceptable discipline and abuse, and Peterson crossed it.

Americans are legally entitled to use “reasonable” force to discipline their children, but the definition of reasonable usually means force that doesn’t injure a child or leave marks.

The larger question is what to think about spanking kids at all, and that’s much less clear.

Spanking has declined, but because all studies rely on self-reporting, the numbers are fuzzy. In 1998, the American Academy of Pediatrics found that 90 percent of parents physically disciplined their kids, and numbers from a 2013 Harris Poll show that 67 percent still do.

Many experts preach that this has troubling effects, including aggression, defiance, violence, depression, and even substance abuse and mental illness. But if those were common results, 90 percent of today’s adults would be a mess.

What’s missing is a sense of proportion. Common sense says most kids who endure a little spanking will do fine, while severe beatings can do lasting harm.

Even the experts disagree about whether spanking is OK. The American Academy of Pediatrics says that because physical punishment can escalate to abuse, parents should use alternative methods such as taking away privileges. But other studies argue that light, quick spanking should remain an option for disciplining young children if other measures meet with defiance.

Who should you believe? That’s obviously for every parent to sort out, within limits that Peterson unwittingly exceeded.

All this has the NFL befuddled. The Minnesota Vikings deactivated him, then reactivated him, then reversed field again. He’s getting paid as his case proceeds.

The league, already reeling from criticism of its tepid handling of player violence, including a brief two-game suspension of running back Ray Rice for knocking his fiancée cold, seems paralyzed.

But the lesson for the NFL, Peterson and frustrated parents is all the same. Discipline is essential, but violence is intolerable.

The answer obviously isn’t to beat Peterson with a switch. It is to give him a timeout — specifically a suspension — along with instruction in how to behave.